Simultaneous grinding machine

ABSTRACT

An apparatus for grinding an elongated workpiece having a plurality of outer surfaces of revolution all centered on a common workpiece axis has a frame and means such as a headstock and tailstock for rotating the workpiece about the workpiece axis. Two grinders on the frame diametrally flank the workpiece axis and are displaceable radially of the workpiece axis. They each have a respective set of axially spaced grinding wheels. Actuator means serves for displacing the grinders in respective diametrally opposite directions for engaging the grinding wheels with the surfaces of the rotating workpiece grinder. The axial spacing and dimensions of the wheels correspond to the axial spacing and dimensions of the surfaces such that all the surfaces of the workpiece can be ground simultaneously.

FIELD OF THE INVENTION

The present invention relates to a grinding apparatus. More particularly this invention concerns an apparatus for grinding a plurality of concentric surfaces of a workpiece.

BACKGROUND OF THE INVENTION

A simultaneous grinding apparatus is used on a workpiece having a plurality of coaxial or concentric surfaces of revolution, for instance the journals of a camshaft. The workpiece is rotated about the workpiece axis on which these surfaces are centered and a set of grinding tools is simultaneously urged radially of the workpiece axis, with each such tool engaging a respective one of the surfaces to be ground. The tools are typically grinding wheels also rotatable about a common tool axis parallel to the grinding axis.

As disclosed in US 2012/0164926, it is known to urge a single grinding tool against the workpiece radially opposite the set of grinding wheels. The purpose of this single tool is to grind a surface for engagement by a steady rest. Thus initially the workpiece is ground from both sides, then the tool grinding the steady rest surface is withdrawn and replaced by a steady rest so that the workpiece is held accurately on center for the rest of the grinding operation, allowing the surfaces being engaged on the other side by the grinding wheels to be finish-ground.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide an improved simultaneous grinding machine.

Another object is the provision of such an improved simultaneous grinding machine that overcomes the above-given disadvantages, in particular that can grind all the concentric surfaces of a workpiece in a single operation from coarse to finish grinding.

SUMMARY OF THE INVENTION

An apparatus for grinding an elongated workpiece having a plurality of outer surfaces of revolution all centered on a common workpiece axis has according to the invention a frame and means such as a headstock and tailstock for rotating the workpiece about the workpiece axis. Two grinders on the frame diametrally flank the workpiece axis and are displaceable radially of the workpiece axis. They each have a respective set of axially spaced grinding wheels. Actuator means serves for displacing the grinders in respective diametrally opposite directions for engaging the grinding wheels with the surfaces of the rotating workpiece grinder. The axial spacing and dimensions of the wheels correspond to the axial spacing and dimensions of the surfaces such that all the surfaces of the workpiece can be ground simultaneously.

In this way most of the radial forces tending to bend or deflect the workpiece are basically canceled out, and it is possible to machine all the surfaces simultaneously with a high degree of precision.

According to the invention each surface of revolution there is at least one respective grinding wheel. More particularly one or two are axially level with one or two of the grinding wheels of the other set so that two of the surfaces are engaged by two grinding wheels. It is also possible for each of the grinding wheels of one of the sets to be axially level with a respective one of the grinding wheels of the other set so that each of the workpiece surfaces is engaged by two grinding wheels. In another arrangement at least one of the grinding wheels of each of the sets is axially between two of the grinding wheels of the other of the sets.

The workpiece according to the invention is a crankshaft and the surfaces include journals between adjacent crankpins and bearing surfaces at ends of the crankshaft, wherein each of the wheels can also engage axially directed faces of flanges carrying the crankpins and flanking the journals. It is not necessary to pre-grind seats for the steady rest.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a small scale partly schematic side elevational view of a simultaneous grinding apparatus according to the invention;

FIGS. 2-5 are detail views of variations on the apparatus of FIG. 1; and

FIG. 6 is a cross-section view of another system according to the invention.

DETAILED DESCRIPTION

As seen in FIG. 1 the simultaneous grinding machine or apparatus according to FIG. 1 has a frame 7 on which are mounted a driven headstock 1 and a tailstock 2 for holding and rotating a workpiece 3, here a camshaft with concentric cylindrical journals 12 and bearings 15 and 16, about a vertical axis A. The headstock 1 and tailstock 2 constitute means for holding the workpiece 3 with its axis A axially and radially fixed relative to the frame 7 while rotating the workpiece 3 about the axis A relative to the frame. Two grinders 6 and 6′ that diametrally flank the axis A are provided for machining the workpiece 3.

The grinders 6 and 6′ are mounted on respective is horizontal slides 5 and 5′ that can move horizontally in a direction x on respective guide rails 20 and 20′ of respective vertical slides 4 and 4′ in turn mounted on respective vertical guide rails 8 and 8′ for movement in a vertical direction z on the frame 7. Respective motors or actuators 9 and 9′ of the ball/spindle type effect the vertical direction-z movement of the slides 4 and 4′ and similar schematically illustrated respective actuators 18 and 18′ serve for shifting the horizontal slides 5 and 5′ in the horizontal direction-x direction on the vertical slides 4 and 4′.

Each grinder 6 and 6′ carries a respective set 10 and 10′ of grinding tools 13 and 13′, here standard cylindrical grinding disks or wheels. The wheels 13 and 13′ are axially spaced along and their cylindrical outer surfaces are centered on respective axes 14 and 14′ parallel to the vertical direction z and diametrally flanking the axis A. The axial spacings of the tools 13 and 13′ along their respective axes 14 and 14′ correspond to the axial spacing of the bearing surfaces 12, 15 and 16 of the workpiece 3, and the diameters of the wheels 13 and 13′ vary complementarily to the diameters of the surfaces 12, 15 and 16.

According to the invention roughly half of the surfaces 12, 15, and 16 are engaged by the tools 13 and the other half by the tools 13′, and the set 10 of tools 13 is diametrally opposite relative to the axis A of the set 10′ of tools 13′. In this manner the radially inwardly directed forces exerted by the tools 13 and 13′ are roughly equal, with the result that the workpiece 3 remains on center on the axis A with no significant radial deflection caused by the forces applied to it by the grinding operation.

FIG. 1 also shows how wheels 13 and 13′ at the ends of the sets 10 and 10′ grind the end bearings 15 and 16, and all of the wheels 13 and 13′ can also serve to machine axially directed side faces of the flanges carrying the crankpins.

There are several manners to further improve the stability of the workpiece 3 according to the invention during machining:

FIG. 2 shows how two tools 13 and 13′ from the sets 10 and 10′ can engage the same journal surface 12, that is a cylindrical surface between two crank pins. Here the surface 12 that is engaged is at or near the axial center of the workpiece 3

FIG. 3 shows an arrangement where two central journals 12 are each engaged by two tools 13 and 13′ as in FIG. 2.

FIG. 4 shows a system where each of the surfaces 12 is engaged by two respective tools 13 and 13′.

FIG. 5 shows a system where the tools 13 and 13′ are axially interleaved, that is at least one tool 13 is between two of the tools 13′ and one of the tools 13′ between two of the tools 13.

Finally FIG. 6 shows a steady rest 17 carried on the frame 7 and urged against the workpiece 3 in a direction perpendicular to a plane defined by the axes A, 14, and 14′. This largely stabilizes the workpiece in a direction tangential to the forces applied to it by the rotating wheels 13 and 13′ turning as indicated by the arrows in opposite directions about the respective axes 14 and 14′. Because of the opposite rotation directions, both wheels 13 and 13′ urge the workpiece 3 in the same tangential direction perpendicular to the plane of the axes A, 14, and 14′ and toward the steady rest 17. This system ensures that the workpiece 3 is very stably centered on the axis A. 

1. An apparatus for grinding an elongated workpiece having a plurality of outer surfaces of revolution all centered on a common workpiece axis, the apparatus comprising: a frame; means on the frame for rotating the workpiece about the workpiece axis; two grinders on the frame diametrally flanking the workpiece axis and displaceable radially of the workpiece axis and each having a respective set of axially spaced grinding wheels; and means for displacing the grinders in respective diametrally opposite directions for engaging the grinding wheels with the surfaces of the rotating workpiece grinder, axial spacing and dimensions of the wheels corresponding to axial spacing and dimensions of the surfaces such that all the surfaces of the workpiece can be ground simultaneously.
 2. The grinding apparatus defined in claim 1, wherein for each surface of revolution there is at least one respective grinding wheel.
 3. The grinding apparatus defined in claim 2, wherein at least one of the grinding wheels of one of the sets is axially level with one of the grinding wheels of the other set so that the respective surface is engaged by two grinding wheels.
 4. The grinding apparatus defined in claim 2, wherein two of the grinding wheels of one of the sets are axially level with two of the grinding wheels of the other set so that two of the surfaces are engaged by two grinding wheels.
 5. The grinding apparatus defined in claim 2, wherein each of the grinding wheels of one of the sets is axially level with a respective one of the grinding wheels of the other set so that each of the workpiece surfaces is engaged by two grinding wheels.
 6. The grinding apparatus defined in claim 2, wherein at least one of the grinding wheels of each of the sets is axially between two of the grinding wheels of the other of the sets.
 7. The grinding apparatus defined in claim 1, wherein the workpiece is a crankshaft and the surfaces include journals between adjacent crankpins and bearing surfaces at ends of the crankshaft, wherein each of the wheels can also engage axially directed faces of flanges carrying the crankpins and flanking the journals.
 8. The grinding apparatus defined in claim 1, further comprising: a steady rest engageable with the workpiece in a direction perpendicular to a plane defined by the workpiece axis and axes about which the wheels are rotated.
 9. An apparatus for grinding an elongated workpiece having a plurality of outer surfaces of revolution all centered on a common workpiece axis, the apparatus comprising: a frame; means on the frame for rotating the workpiece about the workpiece axis; two grinders on the frame diametrally flanking the workpiece axis and displaceable radially of the workpiece axis and each having a respective set of axially spaced grinding wheels; means for displacing the grinders in respective diametrally opposite directions for engaging the grinding wheels with the surfaces of the rotating workpiece grinder, axial spacing and dimensions of the wheels corresponding to axial spacing and dimensions of the surfaces such that all the surfaces of the workpiece can be ground simultaneously; and a steady rest engageable with the workpiece in a direction perpendicular to a plane defined by the workpiece axis and axes about which the wheels are rotated.
 10. The grinding apparatus defined in claim 9, wherein the sets are rotated about respective axes diametrally flanking the workpiece axis in such a direction as to exert tangential forces on the workpiece urging the workpiece against the steady rest. 